WR and MR Series Compared, Field by Field: The Datasheet-Level Walsin WR vs MR Resistor Comparison

Walsin Technology (Walsin)’s WR and MR chip resistor datasheets specify identical dimensions —
L, W, T, Tb and Tt — at every one of the four case sizes they share. What actually separates
them is the qualification programme: the MR automotive datasheet names 16 distinct tests,
against 8 in the WR commercial datasheet, with only 4 tests common to both. Power rating and
export anomalies between the two lines are already covered elsewhere; this post works from the
datasheets themselves.

Venatech Limited, an authorised Walsin distributor in Hong Kong, holds both chip resistor
datasheets Walsin publishes — Walsin_WR_General_Purpose_Chip_Resistor.pdf (ASC_WR_V24,
September 2016) and Walsin_MR_Automotive_Thick_Film_Chip_Resistor.pdf (ASC_MR_V13, March
2024) — alongside all 137 chip resistor export files. We hold no public URL for either PDF; cite
the filename and flag the claim for review if you need to pass it on. This post is the
datasheet-level companion to our catalogue-level comparison of the two lines; see
Walsin automotive chip resistors: MR, SR and the AEC-Q200 split
for the power-rating step, the voltage match, the export anomaly affecting 5,814 MR parts and the
case-size count. None of that is repeated here. Every part number below is real.

Are Walsin WR and MR chip resistors the same physical size?

Yes, at every case size WR and MR share. Both datasheets tabulate length (L), width (W),
thickness (T), bottom termination (Tb) and top termination (Tt) in millimetres, and the figures
match to the same tolerance at 0402, 0603, 0805 and 1206:

Source: Walsin_WR_General_Purpose_Chip_Resistor.pdf page 3 and
Walsin_MR_Automotive_Thick_Film_Chip_Resistor.pdf page 3. The 1210 row exists only on the MR
side, which is the same case-size gap our catalogue-level post already quantifies. Four real
representative parts at 10 kΩ, ±1%: WR04X1002FTL, WR06X1002FTL, WR08X1002FTL,
WR12X1002FTL on the commercial side and MR04X1002FTL, MR06X1002FTL, MR08X1002FTL,
MR10X1002FTL, MR12X1002FTL on the automotive side.

Do WR and MR chip resistors use the same marking scheme?

Yes, letter for letter. Both datasheets print an identical 96-row CODE table mapping a two-digit
code to a three-digit E96 mantissa (01→100, 02→102 … 96→976), and both use the same letter
index for the decade — Y=10⁻², X=10⁻¹, A=10⁰, B=10¹, C=10², D=10³, E=10⁴, F=10⁵.
A 0603 1% part marked 25X reads as CODE 25 (17.8) at decade X, i.e. 17.8 Ω, on both the WR06
and MR06 lines. 0402 on both datasheets carries no marking at all; 1206, 1210 (MR only) and 0805
take 3-digit marking at 5% and Jumper, 4-digit at 1%; 0603 takes 3-digit marking at both
tolerances.

What resistance range and E-series do WR and MR actually cover?

The same nominal range — 1 Ω to 10 MΩ at both 1% and 5% tolerance — but the datasheets word the
E-series claim differently. WR’s functional description states resistance values are “taken from
the E24 series for resistors with a tolerance of 5%, and E96 series for resistors with a
tolerance of 1%.” MR’s matching sentence states “E24 series for resistors with a tolerance of
5%, and E24+E96 series for resistors with a tolerance of 1%” — MR explicitly folds E24 into its
1% range, WR’s wording does not.

For how that resistance range actually splits between E24 and E96 across the full chip resistor
catalogue, including which series groups are E24-only, see
E24 vs E96: which Walsin series give you which. We
have already established, and will not re-derive here, that the TCR band structure itself
differs between the two datasheets — see the next section for the reference to that finding.

How many qualification tests does the MR datasheet specify against WR?

16 against 8. Both datasheets list “Resistance 0” (plain DC resistance measurement) before
naming individual tests; counting only the named tests, MR’s test and requirements pages name
16, WR’s name 8, and only 4 are common to both by name:

That gives MR 12 tests WR does not list and WR 4 tests MR does not list, against 4 shared by
name. The three tests citing an AEC-Q200 method number — board flex, terminal strength and ESD —
appear only on the MR datasheet, which is the closest either PDF comes to naming the standard
directly rather than only the cover-page compliance claim.

Is the TCR band structure the same on both datasheets?

No, and this is a fact Venatech has already published: MR’s TCR table breaks the resistance
range into three bands (≤10 Ω: −200 to +400 ppm/°C; 10 Ω < R ≤ 1 MΩ: ≦±100; above 1 MΩ: ≦±200),
while WR’s table uses two bands (≤10 Ω: −200 to +400; above 10 Ω, read through to 10 MΩ: ≦±100)
with no separate high-ohm step. We are citing that finding here rather than re-deriving it — see
Walsin automotive chip resistors: MR, SR and the AEC-Q200 split
for the full figures and the export counts that follow from it.

Do WR and MR state the same operating temperature and climatic category?

Climatic category yes, operating temperature only partially. Both datasheets state climatic
category 55/155/56 under IEC 60068 for the general resistor line. Both also state “Operation
temperature −55 ~ +155°C” or “Operating Temperature −55 ~ +155°C” — but in both PDFs that line
appears only inside the Jumper (0 Ω) specification table, not in the general quick-reference data
for the resistive parts.

The full range is on the Walsin chip resistor range page, and the
case-size and E-series spread of the wider general purpose group is in
Walsin’s general purpose chip resistor range.

The short version

WR and MR share identical dimensions at every case size they both cover, and an identical
marking and E96 code table. What actually separates them, beyond the power and voltage figures
already published, is the qualification programme: MR names 16 tests including three with an
explicit AEC-Q200 method number, WR names 8, and only 4 are shared by name. Neither datasheet
states an operating temperature for the general resistive line outside the jumper table — treat
that as an open question, not an assumption.

Send us your WR or MR part number and we will map it against both datasheets, field by
field. Or send your automotive BOM and ask which qualification tests actually apply.

Faster than an email. The cross-reference tool takes a pasted list or a spreadsheet and returns Walsin chip resistor candidates field by field, differences included. Ready stock shows what is physically in Hong Kong, so you can see straight away whether a line is a stock pull or a production slot.

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